1. Field of the Invention
The present invention relates to a power tool having a commutator motor, and particularly to the shape of end plates for a rotor in the commutator motor.
2. Description of the Related Art
In Japanese patent application publication No. 2002-186216 discloses the rotor of a commutator motor. As shown in FIG. 1, a rotor 124 of such a commutator motor is provided with end plates 126. In addition to the end plates 126, the rotor 124 includes a rotor shaft 123, a rotor core 125, and a commutator 132. The rotor core 125 is fixed coaxially with the rotor shaft 123 and has rotor core slots 125a. The end plates 126 are coaxially fixed to the rotor shaft 123 on either axial end of the rotor core 125. The commutator 132 is coaxially fixed to the rotor shaft 123 on the side of one end plate 126, and a fan 107 is fixed coaxially to the rotor shaft 123 on the side of the other end plate 126
Each of the end plates 126 includes a plate 129 that contacts the rotor core 125, and a cylindrical shaft insulator 128. Slot parts 129a substantially identical in shape to the rotor core slots 125a are formed in the plate 129 at positions opposing the rotor core slots 125a. Grooves 129b are formed in the plate 129, in communication with adjacent slot parts 129a. 
The rotor core slots 125a and slot parts 129a hold rotor coils 133. The rotor coils 133 include coil side bundles 133A and coil end bundles 133B. A power supply (not shown) supplies an electric current for rotating the rotor 124. The fan 107 rotates simultaneously with the rotor 124, blowing air for cooling the rotor coils 133 in which heat is produced by the electric current. The air passes through the air paths 27 and cools the first and second molded coils 22 and 23 in which heat is generated by the flowing current.
Japanese patent application publication No. HEI-1-283037 discloses another end plate structure for a commutator motor. This end plate includes a cylindrical shaft insulator, and a plate contacting the rotor core and having slot parts formed therein. Protrusions provided on the plate extend along edges of the slot parts toward the non-rotor core side. Protruding parts also protrude radially outward from the shaft insulator.